Green’s Dictionary of Slang

(S.Afr. Und.) a measure of tobacco, about one-40th of an ounce.

1949

H.C. Bosman Cold Stone Jug (1981) II 27: The price of it was high, a single stoppie of dagga being reckoned as the equivalent of twenty doppies [...] of tobacco. [Ibid.] 49: A half-ounce ration of tobacco was divided into twenty ‘doppies’. each about the size of a smoke.